23 August 2011

Irene heading for Bahamas and possibly US

Since my last update on Friday (I apologize for the break during this interesting period... but it was vacation time), the easterly wave that was located far east of the Lesser Antilles has intensified dramatically.  It became TS Irene on Saturday evening, crossed over the Leeward Islands, became the season's first hurricane on Monday morning as it crossed over Puerto Rico, and is now nearing Category 2 intensity as it begins to track over the eastern Bahamas.

The forecast is of course of great interest to the US, since storms in this location can easily hit the US coast (either by tracking westward and entering the Gulf of Mexico or by recurving and hitting the southeastern states).  Models have been strongly trending toward an earlier recurvature, bringing any potential US landfall further and further northward along the coast.  The figure below (from http://rammb.cira.colostate.edu/products/tc_realtime/) shows three models' track forecasts... thick lines for past location, very thin lines for past forecasts (shown only once daily), and medium lines for the most recent forecast.  The feature to note is the older runs are consistently further west than the later runs.

The models are in good agreement for a NC landfall (or near miss offshore) on Saturday night, most likely as a Category 2-3 hurricane.  Before that though, it is causing and will continue to cause substantial problems in the Bahamas (wind, heavy rain, large storm surge, etc).  You can always find the latest official track forecast, watches, and warnings at http://www.nhc.noaa.gov/storm_graphics/AT09/refresh/AL0911W5+gif/205313W_sm.gif

The intensity at the latest advisory is 80kts with a forecast of 110kts in 3-4 days.

Please visit my tropical Atlantic headquarters.

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